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Post  balogh on Sat Nov 16, 2019 11:51 am

I bench tested my favorite reedy the 290 red postage backplate product engine with Kamtechnik's new turbo head made for commercially available turbo plugs.

Fuel is home blended 60/20/20 cocktail. Prop is 5x4 black COX nylon sold by Bernie. ( In reality the stock size of this prop is a bit less maybe 4.8x4).

Ambient temperature about 12 Celsius i.e. 53.6 F. Elevation above sea level around 400 feet.

All original stock parts - except for the turbo head - , beryllium copper star reed, no.1 cylinder..
During the 1st run the plug went loose and oozed aluminum laden grey castor in the thread area that helped diagnose the problem instantly. More torque applied on the wrench and the rurbo plug bottom cone wedged itself in the tapered nest in the head and the leak disappeared.
Kamtechnik turbo head on 290 red postage stamp backplate reedy 15739210

I audiotached the engine and measured 18.6k which is quite something from this reedy..I want to swap my Killer Bee clone on the Lil Roughneck with this engine and wanted to know the rpm difference.
A prior audiotach with a Nelson turbo plug returned basically the same result ( maybe 100..150 rpm less but this may be a normal test reproduction error  between the Kamtechnik and  the Nelson..I figure the 2 heads may bring the same compression ratio and the shape of combustion chambers is very similar if not identical)

5 shims under the head. Fewer shims lead to slight overcompression and overheating. For this medium hot plug 5 shims seem optimal. (Deck level on crankcase seems to be low? I expected the rpm to max out with 3 or 4 shims max..)

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Post  1/2A Nut on Sat Nov 16, 2019 11:55 pm

Good to see you having some fun with your new turbo plug adapter!
I enjoyed reading your feedback on it.

I use after run oil in the threads when seating the first turbo plug to a
adapter. The adapters's plug seat is flexed to fit the turbo plugs face.
The oil helps to allow it to slide on the seat as it warps it to match and
mate for a leak free fit.

During prototype testing the adapters tested were not considered passing until
it could meet or exceed the Nelson plugs performance.  Here are the results that
helped it to go into production:

Tested Kamtechnik Trumpet Turbo Plug Adapter - OS RP6 plug
Both Plugs Tested with the tuned pipe on my NANO X
Each test used 2 gaskets.

4 x 4.5 Static Peak 26,324 rpm / 112 mph pitch speed
.151hp / 113w / 7.8oz thrust
+238 rpm

VS

Galbreath Nelson Head Adapter:
4 x 4.5 Static Peak 26,086 rpm / 111 mph pitch speed
.147hp / 110w / 7.8oz thrust

I had no issues with over heating or over compression on two shims using
a 4x4.5 speed prop. 25% nitro / 20% Look forward to hearing your feedback
when you fly the plane if you noticed any increase in performance.

The turbo plug adapter was then flow with the Nano X


APC 4.3 x 5.5N Speed
Last two passes are the best peak: 28,181 rpm / 147 mph  Prop Pitch Speed
Now the fastest TD .051 3ch plane on You Tube - bested Nano III now in 2nd
Best static 21,962 rpm / 7.1oz thrust / 115 mph pitch speed / Pipe at MRP 7.5"
.144 hp - 107.4w / 7.1 oz thrust / stock piston /cylinder and crank

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Post  balogh on Sun Nov 17, 2019 1:13 am

Thanks Brad. I tried the oil between threads but may not have applied proper torque. Overheating also hit me by surprise.I will re- test with fewer shims. 5 seems too high to me too..Leaking plug in itself may cause overheating - plus of course compression and power loss - due to the high speed at which gases seep along the loose threads and convect their heat to the aluminum head much more, than when simply swirling in the combustion dome. (Simple physics..like when you blow air on your skin in hot sauna and it burns you more than when you just sit around because high speed turbulent flow boosts heat transfer coefficient..).
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Post  1/2A Nut on Sun Nov 17, 2019 3:56 am

Yes a oil film over the aluminum surface can act like a insulator.
What brand plug did you use?

How much run time does that engine have?
With the 5x4 prop should be able to get away with 4 shims.
18,683 rpm 4.8x4: 8.5oz thrust / .099hp - 72w / 71 mph pitch speed.

A mylar reed should pick up some more rpm.

Deck height vs cylinder shim seat you say the crown of the piston was
below the cylinder's seat prior to shims?

I have a few 290 engines.
One has been under resent testing with a carbon 3D printed backplate up to 3 shims.
I was surprised to add extra shims to that engine ran with a Cox high comp plug.
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Post  balogh on Sun Nov 17, 2019 7:18 am

Brad this is a fairly used 290 with excellent compression even if hot. I thought the deck level may be low but checked and the piston top is even with the squish band of cylinder.

Kamtechnik turbo head on 290 red postage stamp backplate reedy 15739910
I will retest it with fewer shims maybe the gas seep around the plug has caused overheating.
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Post  1/2A Nut on Sun Nov 17, 2019 11:10 am

Seems the 290 / #1 cylinder is pretty consistent mine is similar with no shims
the crown of the piston hits level. I should lay a bit of piano wire across to see
if the piston bumps it but never did. Runs good with 3 shims.



*** your engine
- 53.6 F
- Elevation above sea level around 400 feet.
- Fuel is home blended 60/20/20 --- assume 20% castor
- Assume high moisture levels
- Copper reed
- #1 cylinder
- med /cold plug

Rules to follow / conditions imposed on the engine.
*** your engine required needle valve settings.

Higher air temperature: Lean
Lower air temperature: Rich ***
Higher humidity: Lean ***
Lower humidity: Rich
Higher barometric pressure: Rich ***
Lower barometric pressure: Lean
Higher altitude: Lean
Lower altitude: Rich ***
Higher nitro content: Rich ***
Lower nitro content: Lean
Higher oil content: Lean ***
Lower oil content: Rich
Hotter glow plug: Rich
Colder glow plug: Lean ***

Talley's
4 rich
3 lean

Your cold weather condition has more air density the requirement is more shims
as your packing more fuel in the combustion cycle. Colder plug you are retarding
the engine timing creating more compression prior to ignition. Any idea what
your head temp is? 4 or 5 shims is plausible in the summer you can do 3.  

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